Worm-grinding machine



a ch 9 7 H. E. DURKEE WQRM GRINDING MACHINE 7 Sheets-Sheet 1 Filed March28, 1925 I TTORNEY March 29', 1927. H. E. DURKEE WORM GRINDING MACHINE 7Sheets-Sheet 2 Filed March 28, 1925 A TTORIIEY v March 1927' H. E.DURKEE WORM GRINDING MACHINE Filed March 28 1925 7 Sheets-Sheet 5INVENTOR H 6.19MB

A TTORIVEY H. E. DURKEE WORM GRINDING MACHINE March 29, 1927. 1,622,628

Filed March 28. 1925 '7 Sheets-Sheet 4 INVENTUHI 2 1 March- 927 H. E.DURKEE WORM GRINDING MACHINE Filed March 28, 1925 7 Sheets-Sheet 5 WWW,4 TTORNEY -l|| I.. Illlll l l l I I l l v I ll March 29, 1927. E.DURKEE worm enmnme MACHINE Filed March 2 ,1925 '7 Sheets-Sheet 6INVEIITUR l TTURIIEY March 29 1927.

E. LJURKEE WORM GRINDING MACHINE Filed March 28, 1925 7 Sheets-SheetH's/Mignon BY 4 412 ara/Mn Patented Mar. 29, 192.7. I v V UNITED STATESPATENT OFFICE.

HENRY E. DURKEE, F GLASTONBUBY, CONNECTICUT, ASSIGNOR TO PRATT & WHIT-NEY COMPANY, OF NEW YORIL N. Y., A CORPORATION OF NEW JERSEY.

WORM-GRINDING MACHIN E.

Application filed March 28.19211. Serial No. 19,094.

This invention relates to grinding ma chines and particularly to' amachine for grinding the helicoidal surfaces of screw. threads on Wormsor other threaded members. More especially the machine is def signed forgrinding steering worms designed for use on automobiles or other motordriven vehicles. I

An object of the present invention is to provide a machine designed forrapidly grinding steering worms upon both flanks ot\ their screwthreaded portions so that these surfaces may, after the worm has beenhardened, be generated to a high precision.

Another object of the invention is to provide cam means to reciprocatethe table or support carrying the worm being groundpast the abrasivewheel while it is being rotated continuously in one direction, the

rotary movement taking place in timed relation to the reciprocatorymovements of the work supporting member.

Another object of the invention is to provide a main shaft-rotating inone direction at constant speed during operation and hav-. ing drivingmeans for rotating a work carrying spindle at any predetermined rotativespeed relative thereto, and to provide driving means operating throughthe-work spindle for a main cam drum adapted to reciprocate the table orwork supporting member;

Another object. of the invention is to provide a grinding machine havingsimple means for indexing the work spindle permitting multiple startworms to be readily ground in a continuous operation, these meanspreferably being controlled by timing the rotative movement of thespindle relative to the reciprocatory movement of the support and work,so that first'one of the threads will be ground and then the next and soforth.

Another object of the invention is to provide cam actuated means toadvance and withdraw the wheel and wheel head relative to the worm beingground so that it may contact with the work while the table or supportis moving in one directiori and will be entirely disengaged therefromduring movement of the support in the opposite direction.

A still'further object of the invention is i to provide a wheel headangularly adjustable and having a shaft thereon parallel to the wheelspindle adapted to be driven through bevel gears andadapted, by means ofa belt, to rapidly. rotate the Wheel spindle.

lVith these and other objects'in vlew, my

invention consists in the features of construction and operation setforth in the followingspecification and illustrated in the accompanyingdrawings.

In the accompanying drawings annexed hereto and forming a part of thisspecification, I have shown my, invention embodied 1n a grinding machinefor automobile steering worms, but it will be understood that theinvention can be otherwise embodied and that the drawings are not to beconstrued as defining or limiting the scope of the invention, the claimsappended to this specification being relied upon for that purpose.

In'the drawings:

Figure 1 is a front elevation of the complete machine.

' Fig. 2 is a transverse sectional view in elevation taken substantiallyupon line 2-2 of Fig. 1.

Fig. 3 is a sectional view in elevation showing the table reciprocatingcam and rotating means for the work driver.

Fig. 4 is a horizontal sectional view of the work driver and adjacentparts.

Fig. 5 is a sectional view of the main'cam and work rotating means takenupon line 5-5 of Fig. 3.

F ig. 6 is a horizontal view partly in section of the wheel head and thewheel rotating mechanism. I

Fig. 7 is a front elevation of the actuating means for the work rotatingand wheel advancing mechanisms.

Fig. 8 is a sectional view in elevation taken upon line 66 of Fig. 7.

.Fig. 9 is a detail of the actuating means forftlie wheel advancing andwithdrawing mechanism.

1 Fig. 10 is a detail of the pawl and memberon which it is mountedforming partof the wheel advancing and withdrawing mecha- IllSIIl.

Fig. 1 1 is a detail view of the" wheel ad'- vancing' and withdrawingcam and levers head.

Fig. 12 is. a front elevation of the wheelfeeding mechanism, the handwheel being broken away. 1

or table slidable thereon ;.third, a wheel head movable in a directionat right angles to the work supporting table and having an angularlyadjustable rotatable abrasive wheel; fourth, cam means to reciprocatethe table; fifth, continuous rotating means for a work driver orspindle-on the work support on which a worm being ground may be mounted;sixth, means adapted to reciprocate the support in timed relation to therotations of the work driver; seventh, cam

means to advance and" withdraw the wheel and wheel head relative to theworm being ground-in timed relation to the reciprocations of thesupporting means; and eighth, means to feed the wheel relative to theworm being ground at predetermined intervals during the cycle ofoperations of the machine.

Referring more in particular to the figures of. the drawings, I providea base 10 having a table or work supporting means 11 thereon adapted toslide longitudinally of the base 10 upon suitable ways 12 and 13. Inrear of the table 11 and adapted to slide upon ways 14 extending atright angles to the ways 12 and '13 for the table 11 is a wheel head 15on which is adjustably mounted an abrasive wheel 16. .The means fordriving and positioning the wheel 16 will presently be more fullydescribed. On the table 11 are mounted work supporting and rotatingmeans. These, in the embodiment of the invention illustrated, comprise afit headstock 17 provided with a fixed center 18 and work driving member19 and a tailstock 20 having a center spindle 21 in alignment with theheadstock center 18. The worm W being ground may therefore be supportedupon a fixed axis and will be reciprocated by the sliding movements ofthe table 11 and rotated with the driver 19.

Preferably the supporting table 11 on it's under side is provided with alongitudinally extending shaft 22 rotatably mounted -in suitablebearings and held from end-wise movement relative to the table 11. Thisshaft 22 is adapted to be constantly rotated at any desired speed duringoperation through driving connections from a main driving shaft 23. Thedriving connections between shafts 23 and 22 comprise gears 24 some ofwhich may be changed to vary the rotative speed of the shaft 22 relativeto shaft 23. A spiral gear 25 splined to the shaft 22, so that itremains in fixed position during reciprocations of the table 11, isprovided which meshes with one of the driving gears 24. On this shaft 22also is a gear 26 in mesh with an idler 27 supported upon the table 11which in turn is in mesh with a gear 28 on the work supporting anddriving member 19. From Fig. 3 it will be clearly seen that the drivinggear 28 is mounted upon a sleeve 29 surrounding the spindle 30, thissleeve 29 having a driving dog 31 outstanding therefrom for engagementwith a dog on the worm W being ground. The spindle 30, which may benonrotatable, isprovided with the center 18 upon which one end ofthework being ground may be mounted.

Adjacent the gear 28 for rotating the driver 19 is another gear 32adapted to mesh with a gear 33 on an intermediate driving shaft 34. Thisdriving shaft 34 through geared connections is adapted to rotate a maincam drum 35 for reciprocating the table 11. The driving connections forthis cam drum 35 are very clearly shown in Figs. 3, 4 and 5. Preferably,and as shown in Figs. 3 and 4 a differential driving mechanism 36 isinterposed in the drive for the cam 35 so that the rotative position ofthe cam 35 may be manually varied relative to that of the driver 19during operation. This differential comprises a rotatable memher orhousing 36 which may be rotated by a worm 37 engaging a worm wheel 38cut into its periphery. The worm 37 as shown in Fig. 5 is on a shortforwardly extending shaft 39 having a hand wheel 40 on its forward end.Rotation therefore of the hand wheel 40 will rotate the housing 36 andparts enclosed therein.

Within this housing 36 is an intermediate shaft 41 having a compoundgear 42 thereon, one member of this compound gear engages a gear 43 on.the shaft 34 and the other member with another gear 44 on a secondintermediate driving shaft 45. This last intermediate driving shaft 45is provided with a gear 46 at its outer end adapted to mesh with anidler gear 47 in mesh with a gear 48 on the shaft carrying the main camdrum 35. Preferably these last mentioned gears 46, 47 and 48 are mountedso that they may be readily changed enabling the cam drum 45 to bedriven at any predetermined rotative speed relative to that of the workrotating member 19. It will be seen too that the cam drum 35 will berotated always in the same direction from and in timed relation to therotation of the work supporting and rotating member 19.

The main cam drum 35 is provided with a peripheral groove 48 ofgenerally heli- IIH eoidal form which is adapted to be engaged by aroller 49. The mounting for this cam engaging roller 49 is clearly shownin Fig. and preferably comprises a short shaft 50 suitably mounted uponball bearings and fixed permanently in position in the base 10. It willbe seen therefore that rotation of the cam drum 35 will reciprocate thetable 11 and head and tailstocks 17 and 20 back and forth enabling thework W being ground to be traversed axially simultaneously with itsrotative movement. By means of the housing 36 the cam drum may berotated relative to the work driver 19. Rotating the worm 37 by the handwheel 40 rotates the housing 36 and the compound gear 42 mountedtherein. This therefore rotates the intermediate driving shaft 45 andtherefore the cam drum 35. Normally during operation the housing 36 isstationary but can be rotated at any time to vary the rotative positionof the cam drum 35 relative to the work W and thus vary the relativeaxial positions of the work W and the wheel 16 to fjustify the threadswith the abrasive wheel,

The wheel support 15 comprises a body member 52 adapted to slide uponthe ways 14 provided in the top surface of the base If). these as statedabove extend in a direction normal to those upon which the table 11slides. This body member 52 is provided with an opening in which asleeve 53 is mounted so that the sleeve may be angularly adjusted. Aflange 53 on the forward portion of this sleeve 53 enables it to befastened directly to the body member 52 of the support 15 in anyrotative position of the sleeve. Also upon the forward end surface ofthe sleeve 53 a wheel head 54 is mounted within which a wheel carr ingspindle 55 is rotatably mounted. lhis spindle 55, as shown in Fig. 6, isprovided with a pulley 56 for driving it and with the abrasive wheel 16mounted adjacent one end.

In rear of the sleeve 53 and suitably fastened thereto so that it-may beangularly adjusted with the sleeve, isan annular member 57 carryingbearings for a transverse shaft 58, This shaft 58 is provided with apulley 59 for a belt 60 adapted to pass over and drive the pulley 56 onthe wheel spindle 55. At an intermediate point on this transverse shaft58 is a bevel gear 61 keyed thereto and adapted to mesh with acorresponding bevel gear 62 on the forward end of a rearwardly extendingshaft 63. A pulley 64 on this rearwardly extending shaft 63 providesmeans for rotating it from the main driving shaft 23. Preferably and asshown in Fig. 2, this rearwardly extending shaft 63 ma be carried in aseparate member boltec directly to the body member 52 of the wheelsupport 15. It will be seen from the above described parts that By meansof the angularly adjustable head 54 on which the wheel spindle 55 andwheel 16-are mounted, the wheel spindle 55 may be angularly adjusted toproperly engage the worm W being ground. In

making angular adjustments of the wheel spindle 55, no interruption tothe drlving means for the wheel 16 takes place and no ad ustments of thedriving constructions are necessary.

In order to advance and withdraw the wheel slide 15 and wheel 16 intoand out of operative position, a nut 60 is mounted on the lower surfaceof the wheel supporting slide 15 adapted to be engaged by a screw 61rotatably mounted and axially movable within the base 10. These areshown clearly in Fig. 2. This screw 61 is provided with opposed collars62 between which a yoke member 63 may be disposed adapted to be engagedby a lever 64 pivotally mounted upon a stud 65 within the base 10.Oscillation of this lever 64 by means of a pull rod 66 enables the screw61 to be bodily moved forwardly or rearwardly of the machine and thusmove the wheel 16 and attached parts. The means for oscillating thelever 64 to advance and withdraw the wheel 16 during operation willpresently be described.

In order to adjust the position of the wheel 16. toward or from the workbeing ground for feeding during operation or for adjusting for differentdiameters of worms, means are provided to rotate the screw 61. For thispurpose a gear 67 is provided on the forward end of the screw 61 adaptedto mesh with an elongated pinion 68 so that the gear 67 Will always bein mesh with its pinion 68 in all positions ofthe lever 64 and screw 61.By means of a shaft 69 on which this pinion 68 is carried, and whichextends adjacent the forward vertical surface of the base 10, the screw61 may be rotated stepby step either manually or automatically by thereciprocatory movements of the table 11. Preferably the pinion shaft- 69at its forward end is rovided with a gear 70 in mesh with a gear 71 on ashort shaft 7 2 extending to the front of the machine. On the forwardend of this short shaft 72 are mounted the hand wheel 73 for manuallyadjusting the position of the wheel 16 and the ratchet wheel 74 forfeeding it either manually or automatically. These means for rotatingthe shaft- 72 are more clearly shown in Figs. 12 and 13. On the forwardend of this short shaft 72 1s a .large ratchet wheel 74 adapted to beengaged by a pawl 75 pivot-ally mounted on a hand lever 76. Oscillationof this hand lever 76 will therefore rotate the ratchet wheel 74slightly and therefore rotate the screw 61 through a very small angle.Preferably, movement of the hand lever 76 is limited by an extension 7 7formed integrally on the lever 76 engaging an adjustable stop 78oi'itstanding from the base 10. 78, as shown in Figs. 12 and 13,comprlses a small screw, the forward end of which is adapted to beengaged by the extension 77. In order to feed the wheel 16 automaticallyduring operation of the machine, a bell crank 80 is pivotally mountedupon the base 10, one arm of which is provided with a roller 81 adaptedto be engaged by dogs 82 adjustably positioned on the front surface ofthe table 11. Engagement of the bell crank 80 with one or the other ofthese dogs 32 oscillates it and thus oscillates the extension 77 bymeansof a rod 83 attached to the other arm of the bell crank 80 and engagingthe extension 77 on the lever 76. Preferably, a spring 84 is adapted tobe compressed by movement of these means in one direction and the bellcrank 80 and pawl 7 5 are held in their retracted positions by spring 84which surrounds an extended por-' tion of the rod 83.

The main driving shaft for the machine above referred to comprises aforwardly extending shaft 23 rotatably mounted Within the base 10 andhaving a driving pulley 90 near its rear end. Adjacent the main drivingpulley 90 is the pulley 67 for driving the wheel 16 over which operatesthe belt 66 passing over the pulley 64 on the wheel support 15. On theextreme forward end of shaft 23 is a gear 91 adapted to mesh with thefirst of the train of gears 24 for rotating the shaft 22. The last gearof the train 24 drives a spiral gear on the shaft 22 below the worksupporting table 11 as has been above described. By these means the workW may be rotated at various speeds and the cam dr'um also rotated tovary the speed of reciprocation of the table 11.

Also on the main driving shaft23 at an intermediate point is drivinggear 92 which, through a compound gear 93, drives agear 94 on aconstantly rotating cam shaft 95 for actuating the wheel withdrawing andadvancing mechanism. Preferably on the main driving shaft 23 is a clutch96 so that the forward section of the driving shaft on which are mountedthe gears 91 and 92 may be stopped or started independently of the partcarrying the pulleys 90 and 67. This clutch is shown in Figs. 2 and 8and may be act Hated by a lever 97 connected to a yoke This stop 98engaging a movable member on the clutch.

The driven gear 94 is preferably mounted on a sleeve 99 formedintegrally with a ratchet wheel 100 which is therefore constantlyrotated with the driving shaft 23.

and ear 9.4 are rotatably mounted carries a mem r 102 on which .a pawl103 is pivotally mounted. TlilS pawl 103 is'adapted to be engaged ordisengaged relative to the ratchet wheel 100 by means presentlly to bedescribed. Rotation of the gear 94 ant shaft 101 when the pawl 103 is inengagement with the ratchet wheel 100 rotates acam drum 104. A roller105 on a pivoted arm 106 engages a peripheral groove 107 on this camdrum 104 so that rotation ofthe drum 104 oscillates the arm 106;Preferably the arm 106 is mounted on an oscillating shaft 108, thisshaft 108'also having an upwardly extending arm 109. At the upper end ofthe arm 109 is attached the pull rod 66 for moving the wheel support 15to control the movements of the wheel 16 into-and out of engagementwiththe work being ground.

The shape-70f the groove 107 in the cam drum 104 is such thatapproximately onehalf a revolution will oscillate the pivoted arm 106from one extreme position to the other. Preferably a counterweight 110is supported within the base 10, its supporting cable 111 passing overan idler and being attached to a part of the wheel supporting slide 15.This weight 110 normally holds the wheel slide 15 as far forward aspossible and assists the cam 104 in advancing the wheel 16 toward thework and retaining it positively in that position during grinding.

To control the rotative movement of the cam drum 104 means are providedto control the position of the pawl 103 so that it may be withdrawn fromoperative relation with the ratchet wheel 100 at predetermined positionsor allowed to engage therewith and therefore rotate the shaft 101 andcam 104. The pawl 103 carried by its member 102 is normally oscillatedto its engaging position by a spring 112 shown in Fig. 10. Adapted toengage a rearward extension of the pawl 103 are levers 114 pivotallymounted so that they may be moved into or out of engaging position.Means are provided so that when one lever 114 is moved to disengagingposition, the other one remains in a position where it will be engagedby the pawl 103 upon approximately onehalf a revolution of the member102. As shown in Fig. 7 the levers 114 contacting with the pawl 103 aremounted on short shafts 115 which have fastened to their forward endslevers 116 adapted to be engaged and oscillated by a central lever 117pivotally mounted at its upper end and dis- 'A shaft 101 on whichtheratchet wheel 100 p oscillate this central lever 117 it is miide ofbell-crank form, as will be seen in Fig. 1,

the opposite arm of which is attached to a rod 11.8. The opposite end ofthe rod 118 is fastened to a lever 119 adapted to be engaged andoscillated by adjustable dogs 120 on the table 11.

Contact of the lever .119 with one of the dogs 120 oscillates one of thepawl engaging levers 114 so that it is moved to its disengaged ratchetwheel 100 by the opposite lever 11.4.. .The cam drum 104 is then heldfrom rotation until, by reason of the movement of the table 11 in theopposite'direction, the lever 119 is engaged andoscillated in theopposite direction by the opposite dog 120. This disengages the oppositemember 114 from the pawl 103 thus enabling it to engage a ratchet toolon wheel 100 and rotate the cam drum 104 another fraction of a turn whenthe pawl 103 engages the first lever 114 and is again disengaged. Thus,by engagement of the lever 119 with the dogs 120 alternately near theends of the table movement in each direction, the wheel 10 is advancedor withdrawn from the work. By attaching the rod 118 to one or the otherarms of the dog engaging lever 119 the advancing movement of the wheel10 takes )lace at either end of the table movement. lhe grindingoperation may therefore take place while the table 11 is moving ineither direction.

What- I claim is:

1. A worm grinding machine comprising in combination, a base, worksupporting means slidably mounted thereon, an angularly adjustable wheelhead movable toward and from the su )porting means and having arotatable abrasive wheel therein, a constantly rotatingshaft, a camthereon for reciprocating the work supporting means, and means forrotating the work simultaneously with the reciprocatory movements of thework supporting means.

2. A worm grinding machine comprising in combination, a base, worksupporting means slidably mounted thereon, a wheel headadjustable towardand from the work supporting meansand having a rotatable abrasive wheeltherein, a constantly rotating shaft, a cam driven by said shaft forreciprocating the work supporting means, and means for rotating the worksimultaneously with and in timed relation to the reciprocatory movementsof the work supporting means,

A worm grinding machine comprising in combination, a base, worksupporting means slidably mounted thereon, a wheel head adjustabletoward and from the work supporting means and having a rotatableabrasive wheel therein, a constantly rotating shaft, a "am driven bysaid shaft for reciprocating the work supporting means, and means alsooperated by said shaft for rotating the work simultaneously with and in'timed relation to the reciprocatory movements of the work supportingmeans. i

4. A worm grinding machine comprising in combination, a base, worksupporting means slidably mounted thereon, a wheel head adjustabletoward and from the work supporting means and having a rotatableabrasive wheel therein, a constantly rotating shaft mounted on andmovable with the supporting means, a cam driven by said shaft forreclprocating the work supporting means, and means operated by saidshaft for rotating the work simultaneously with and in timed relation tothe reciprocatory movements of the work supporting means.

A worm grinding machine con'lprising in combination, a base, worksupporting means slidably mounted thereon, a wheel head adjustabletoward and from the work supporting means and having a rotatableabrasive wheel therein, a constantly rotating shaft, means operated bysaid shaft for rotating the work, acam driven by the work rotating meansfor reciprocating the work supporting means whereby the reciprocatorymovements of the work supporting means take place simultaneously and intimed relation with the rotation of the work and means to vary therotative movement of the work supporting means relative to itsreciprocatory movement.

(3. A worm grinding machine comprising in combination, a base, worksupporting means slidably mounted thereon, a wheel head adjustabletoward and from the work supporting means and having a rotatableabrasive wheel therein, cam means toreciprocate'the work supportingmeans past the wheel, means to rotate the work simultaneously with andin timed relation to its reciprocations, means to advance and withdrawvthe wheel in timed relation to the reciprocatory and rotary movementsof the work supporting means. and means to vary the rotative movement ofthe work supporting means relative to its reciproeatory 1n0vement.

7. A. worm grinding machine comprising in combination, a base, worksupporting means slidably mounted thereon, a wheel head having arotatable abrasive wheel therein, cam means rotatably mounted on saidsupporting means to reciprocate the work supporting means past theWheel, meansto rotate the work in timed relation to its reciproeations,and means to advance and withdraw the wheel in timed relation to thereciprocatory movements of the work supporting means.

8. A worm grinding machine compris ng in combination, a base, worksupportlng means slidably mounted thereon. a wheel head having arotatable abrasive wheel therein, cam means to reciprocate the worksupporting means past the wheel, means to advance and withdraw thewheel, and means to continuously rotate the work in the same directionduring the reciprocatory movements of the work supporting means.

5). A worm grinding machine comprising in combination. a base. worksupportin g means slidably mounted thereon, a wheel head .having arotatable abrasive wheel therein. cam means to reciprocate the worksupporting means past the wheel. means to advance and withdraw thewheel, means to continuously rotate the work during the reciprocatorymovements of the work supporting means, 'and means to vary the rotativeand reciprocatory movements.

10. A worm grinding machine comprising in combination, a base. worksupporting means slidably'mounted thereon. a wheel head having arotatable abrasive wheel therein. cam means to reciprocate the worksupporting means past the wheel, means to advance and withdraw thewheel, and means to continuously rotate the work during thereciproeatory movements of the work supp rting means, said cam meansbeing rolated by said work rotating means and in timed relation thereto.

l1. worm grinding machine comprising in combination, a base, worksupporting means slidably mounted thereon, a wheel head having arotatable abrasive wheel therein, cam means mounted on said worksupporting means to reciprocate the work supporting means past thewheel, means to advance and Withdraw the wheel, and means tocontinuously rotate the work during the reeiprocatory movements of thework supporting means.

12. A worm grinding machine comprising in combination, a base, worksupporting means slidable thereon, work rotating means on saidsupporting means, a cam shaft rotatably mounted on said supportingmeans, driving means for said work rotating means, a peripheral cam onsaid shaft adapted to engage a fixed member on said base wherebyrotation of said shaft will recipro- (ate said supporting means, andgear means driven from said work spindle to rotate the cam shaft intimed relation to the rotation of the work.

13. A worm grinding machine comprising in combination, a base, worksupporting means slidable thereon, work rotating means on saidsupporting means, a cam shaft rotatably mounted on said supporting meansand slidable therewith, driving means for said work rotating means, aperipheral cam on said shaft adapted to engage a fixed memher on thebase whereby rotation of said shaft will reciprocate said supportingmeans, means to rotate the work at predetermined variable speeds, andmeans driven from said work spindle to rotate the cam shaft.

14:. A worm grinding machine comprising in combination, a base, worksupporting means slidable thereon, work rotating means on saidsupporting means, a cam shaft rotatably mounted on said supporting meansand slidable therewith, driving means for said work rotating means, aperipheral cam on said shaft adapted to engage a fixed memher on thebase whereby rotation of said shaft will reciprocate said supportingmeans, means to rotate the work at predetermined variable speeds, meansdriven from said work spindle to rotate the cam shaftin timed relationthereto, and means to vary said last named means.

15. A worm grinding machine comprising in combination, a base, worksupporting means slidably mounted thereon, a wheel head having arotatable abrasive wheel therein, a cam for reciprocating the worksupporting means, means for rotating the work simultaneously with thereciprocatory movements of the work supporting means, and means formanually varying the angular positions of'said cam and work rotatingmeans.

1677i worm grinding machine comprising in combination, a base. .worksupporting means slidably mounted thereon, a wheel head having arotatable abrasive wheel therein, a cam for reciprocating the worksupporting means. means for rotating the work simultaneously with thereciprocatory movements of the work supporting means, and a differentialdriving mechanism disposed between said work rotating and supportreciprocating means.

17. A worm grinding machine comprising in combination, a base. worksupporting means slidably mounted thereon. a wheel head having arotatable abrasive wheel therein, a cam for reciprocating the worksupporting means, means for rotating the work simultaneously with thereciproeatory movements of the work supporting means. a differentialdriving mechanism disposed between said work rotating and supportreciprocating means, and means to manually adjust said differentialmeans during operation of the machine. 1

In testimony whereof, I hereto afiix my signature.

HENRY E. DURKEE.

